
// Logic includes
#include "vtkDataIOManagerLogic.h"

// MRML includes
#include "vtkCacheManager.h"
#include "vtkMRMLStorageNode.h"
#include "vtkMRMLStorableNode.h"
#include "vtkPermissionPrompter.h"
#include "vtkMRMLScene.h"
#include <vtkURIHandler.h>

// VTK includes
#include <vtkCallbackCommand.h>
#include <vtkNew.h>
#include <vtkObjectFactory.h>

// VTKsys includes
#include <vtksys/SystemTools.hxx>

// ITKsys includes

// STD includes
#include <cassert>

#ifdef linux
# include "unistd.h"
#endif

#ifdef _WIN32
#else
# include <sys/types.h>
# include <unistd.h>
#endif

//----------------------------------------------------------------------------
#ifndef vtkSetAndObserveDataIOManagerEventsMacro
# define vtkSetAndObserveDataIOManagerEventsMacro(node, value, events)                                          \
   {                                                                                                            \
     vtkObject* _oldNode = (node);                                                                              \
     this->GetDataIOObserverManager()->SetAndObserveObjectEvents(vtkObjectPointer(&(node)), (value), (events)); \
     vtkObject* _newNode = (node);                                                                              \
     if (_oldNode != _newNode)                                                                                  \
     {                                                                                                          \
       this->Modified();                                                                                        \
     }                                                                                                          \
   };
#endif

vtkStandardNewMacro(vtkDataIOManagerLogic);

typedef std::pair<vtkDataTransfer*, vtkMRMLNode*> TransferNodePair;

//----------------------------------------------------------------------------
vtkDataIOManagerLogic::vtkDataIOManagerLogic()
{
  this->DataIOManager = nullptr;

  this->DataIOObserverManager = vtkObserverManager::New();
  this->DataIOObserverManager->GetCallbackCommand()->SetClientData(this);
  this->DataIOObserverManager->GetCallbackCommand()->SetCallback(vtkDataIOManagerLogic::DataIOManagerCallback);
}

//----------------------------------------------------------------------------
vtkDataIOManagerLogic::~vtkDataIOManagerLogic()
{
  if (this->DataIOManager)
  {
    this->SetAndObserveDataIOManager(nullptr);
    if (this->DataIOManager)
    {
      this->DataIOManager->Delete();
      this->DataIOManager = nullptr;
    }
  }
  if (this->DataIOObserverManager)
  {
    this->DataIOObserverManager->Delete();
  }
}

//----------------------------------------------------------------------------
void vtkDataIOManagerLogic::PrintSelf(ostream& os, vtkIndent indent)
{
  this->vtkObject::PrintSelf(os, indent);
  os << indent << "DataIOManager: " << this->GetDataIOManager() << "\n";
}

//----------------------------------------------------------------------------
vtkObserverManager* vtkDataIOManagerLogic::GetDataIOObserverManager()
{
  return this->DataIOObserverManager;
}

//----------------------------------------------------------------------------
void vtkDataIOManagerLogic::DataIOManagerCallback(vtkObject* caller, unsigned long eid, void* clientData, void* callData)
{
  vtkDataIOManagerLogic* self = reinterpret_cast<vtkDataIOManagerLogic*>(clientData);
  assert(vtkDataIOManager::SafeDownCast(caller));
  self->ProcessDataIOManagerEvents(caller, eid, callData);
}

//----------------------------------------------------------------------------
void vtkDataIOManagerLogic::ProcessDataIOManagerEvents(
#ifndef NDEBUG
  vtkObject* caller,
#else
  vtkObject* vtkNotUsed(caller),
#endif
  unsigned long event,
  void* callData)
{
  assert(vtkDataIOManager::SafeDownCast(caller));
  vtkMRMLNode* node = reinterpret_cast<vtkMRMLNode*>(callData);
  // ignore node events that aren't volumes or slice nodes
  if ((node != nullptr) && (event == vtkDataIOManager::RemoteReadEvent))
  {
    vtkDebugMacro("ProcessMRMLEvents: calling queue read on the node " << node->GetID());
    this->QueueRead(node);
    node->InvokeEvent(vtkDataIOManager::RefreshDisplayEvent);
  }
  else if ((node != nullptr) && (event == vtkDataIOManager::RemoteWriteEvent))
  {
    vtkDebugMacro("ProcessMRMLEvents: calling queue write on the node " << node->GetID());
    this->QueueWrite(node);
    node->InvokeEvent(vtkDataIOManager::RefreshDisplayEvent);
  }
}

//----------------------------------------------------------------------------
void vtkDataIOManagerLogic::SetAndObserveDataIOManager(vtkDataIOManager* iomanager)
{
  vtkNew<vtkIntArray> events;
  events->InsertNextValue(vtkDataIOManager::RemoteReadEvent);
  events->InsertNextValue(vtkDataIOManager::RemoteWriteEvent);
  events->InsertNextValue(vtkDataIOManager::LocalReadEvent);
  events->InsertNextValue(vtkDataIOManager::LocalWriteEvent);
  vtkSetAndObserveDataIOManagerEventsMacro(this->DataIOManager, iomanager, events.GetPointer());
}

//----------------------------------------------------------------------------
void vtkDataIOManagerLogic::AddNewDataTransfer(vtkDataTransfer* dt, vtkMRMLNode* node)
{
  if (this->GetDataIOManager() != nullptr)
  {
    this->GetDataIOManager()->AddNewDataTransfer(dt, node);
  }
}

//----------------------------------------------------------------------------
void vtkDataIOManagerLogic::DeleteDataTransferFromCache(vtkDataTransfer* dt)
{
  if (dt != nullptr)
  {
    vtkDataIOManager* dm = this->GetDataIOManager();
    if (dm)
    {
      vtkCacheManager* cm = dm->GetCacheManager();
      if (cm != nullptr)
      {
        if (cm->CachedFileExists(dt->GetDestinationURI()))
        {
          cm->DeleteFromCache(dt->GetDestinationURI());
          dt->SetTransferCached(0);
          cm->InvokeEvent(vtkCacheManager::CacheDeleteEvent);
        }
      }
    }
  }
}

//----------------------------------------------------------------------------
void vtkDataIOManagerLogic::ClearCache()
{
  vtkDataIOManager* dm = this->GetDataIOManager();
  if (dm)
  {
    vtkCacheManager* cm = dm->GetCacheManager();
    if (cm != nullptr)
    {
      cm->ClearCache();
      dm->AllTransfersClearedFromCache();
      cm->InvokeEvent(vtkCacheManager::CacheClearEvent);
    }
  }
}

//----------------------------------------------------------------------------
void vtkDataIOManagerLogic::CancelDataTransfer(vtkDataTransfer* dt)
{
  if (dt != nullptr)
  {
    dt->SetCancelRequested(1);
    dt->SetTransferStatus(vtkDataTransfer::CancelPending);
  }
}

//----------------------------------------------------------------------------
int vtkDataIOManagerLogic::QueueRead(vtkMRMLNode* node)
{
  //  this->DebugOn();
  //--- do some node nullchecking first.
  if (node == nullptr)
  {
    vtkErrorMacro("QueueRead: null input node!");
    return 0;
  }
  vtkMRMLStorableNode* dnode = vtkMRMLStorableNode::SafeDownCast(node);
  if (dnode == nullptr)
  {
    vtkErrorMacro("QueueRead: unable to cast input mrml node " << node->GetID() << " to a storable node");
    return 0;
  }

  if (dnode->GetStorageNode() == nullptr)
  {
    vtkErrorMacro("QueueRead: unable to get storage node from the storable node " << dnode->GetID() << ", returning");
    return 0;
  }
  //--- find the storage node that's in the scheduled state
  int numStorageNodes = dnode->GetNumberOfStorageNodes();
  int storageNodeIndex = -1;
  int numScheduledNodes = 0;
  for (int n = 0; n < numStorageNodes; n++)
  {
    if (dnode->GetNthStorageNode(n)->GetReadState() == vtkMRMLStorageNode::Scheduled)
    {
      vtkDebugMacro("QueueRead: found storage node in scheduled state, n = " << n);
      if (storageNodeIndex == -1)
      {
        storageNodeIndex = n;
      }
      numScheduledNodes++;
    }
  }
  vtkDebugMacro("QueueRead: there are " << numScheduledNodes << " storage nodes scheduled to be read on " << node->GetID());
  if (storageNodeIndex == -1)
  {
    vtkDebugMacro("QueueRead: no storage nodes found in scheduled state, checked " << numStorageNodes);
    return 0;
  }
  else
  {
    // set it to working, the storage node will wait to read until it's ready
    // (ApplyTransfer will set it to ready when it's done)
    vtkDebugMacro("QueueRead: setting " << storageNodeIndex << " storage node read state to working, uri = " << dnode->GetNthStorageNode(storageNodeIndex)->GetURI());
    dnode->GetNthStorageNode(storageNodeIndex)->SetReadStateTransferring();
  }

  //--- if handler is good and there's enough cache space, queue the read
  vtkURIHandler* handler = dnode->GetNthStorageNode(storageNodeIndex)->GetURIHandler();
  if (handler == nullptr)
  {
    vtkErrorMacro("QueueRead: null URI handler!");
    return 0;
  }
  else
  {
    vtkDebugMacro("QueueRead: got the handler");
  }
  if (this->DataIOManager == nullptr)
  {
    vtkErrorMacro("QueueRead: DataIOManager is null");
    return 0;
  }

  vtkCacheManager* cm = this->GetDataIOManager()->GetCacheManager();
  if (cm == nullptr)
  {
    vtkErrorMacro("QueueRead: CacheManager is null");
    return 0;
  }

  const char* source = dnode->GetNthStorageNode(storageNodeIndex)->GetURI();
  const char* dest = cm->GetFilenameFromURI(source);
  vtkDebugMacro("QueueRead: got the source " << source << " and dest " << dest);

  //--- set the destination filename in the node.
  dnode->GetNthStorageNode(storageNodeIndex)->SetFileName(dest);

  // -- now loop over any uri list and set the filenames
  dnode->GetNthStorageNode(storageNodeIndex)->ResetFileNameList();
  bool allCachedFilesExist = true;
  for (int uriNum = 0; uriNum < dnode->GetNthStorageNode(storageNodeIndex)->GetNumberOfURIs(); uriNum++)
  {
    const char* sourceN = dnode->GetNthStorageNode(storageNodeIndex)->GetNthURI(uriNum);
    if (sourceN)
    {
      const char* destN = cm->GetFilenameFromURI(sourceN);
      if (destN)
      {
        dnode->GetNthStorageNode(storageNodeIndex)->AddFileName(destN);
        vtkDebugMacro("QueueRead: set " << uriNum << " filename to " << destN << ", source uri = " << sourceN);
        // check if it exists
        if (!cm->CachedFileExists(destN))
        {
          allCachedFilesExist = false;
        }
      }
    }
  }
  //---
  //--- WJPtest:
  //--- Again, test for space to download the file.
  //--- This test has been done in MRML (DataIOManager), but with asynchIO,
  //--- Cache may have become full since the remote read was queued.
  //---
  float bufsize = (cm->GetRemoteCacheLimit() * 1000000.0) - (cm->GetRemoteCacheFreeBufferSize() * 1000000.0);
  if ((cm->GetCurrentCacheSize() * 1000000.0) >= bufsize)
  {
    //--- No space left in cache.
    if (cm->CachedFileExists(dest))
    {
      //--- Load the cached version as a last resort.
      dnode->GetNthStorageNode(storageNodeIndex)->SetReadStateTransferDone();
    }
    else
    {
      //--- Mark the node's read state as cancelled.
      dnode->GetNthStorageNode(storageNodeIndex)->SetReadStateCancelled();
    }
    //--- Invoke an event that will trigger GUI to post
    //--- a message box telling if one hasn't been posted already
    //--- user that there's insufficient space in the cache,
    //--- to download new data, but that Slicer is loading
    //--- a cached version IF one is available.
    if (cm->GetInsufficientFreeBufferNotificationFlag() == 0)
    {
      cm->InvokeEvent(vtkCacheManager::InsufficientFreeBufferEvent);
      cm->SetInsufficientFreeBufferNotificationFlag(1);
    }
    return 1;
  }
  //---
  //---END WJPtest

  ///---
  //--- if the filename already exists in cache and
  //--- user has selected not to redownload cached files
  //--- just return.
  if ((cm->CachedFileExists(dest)) && //
      allCachedFilesExist &&          //
      (!(cm->GetEnableForceRedownload())))
  {
    dnode->GetNthStorageNode(storageNodeIndex)->SetReadStateTransferDone();
    vtkDebugMacro("QueueRead: the destination file is there and we're not forcing redownload");
    return 1;
  }

  //--- Otherwise, just do the data transfer whether
  //--- the file already exists in cache or not
  //--- (download or redownload)
  //---
  //--- TODO: build out the logic to handle creating
  //--- new versions of the dataset in cache.

  //--- if permissions are required, invoke the permissions prompter.
  int retval = -1;
  if (handler->GetPermissionPrompter() != nullptr)
  {
    while (retval < 0)
    {
      //--- keep prompting until user provides all information, or user cancels.
      retval = handler->GetPermissionPrompter()->Prompt(nullptr);
    }
  }
  if (retval == 0)
  {
    //--- no permission fields were completed.
    //--- Transfer should be cancelled -- how do we do this?
    dnode->GetNthStorageNode(storageNodeIndex)->SetReadStateCancelled();
    vtkDebugMacro("QueueRead: cancelling data transfer.");
    return 0;
  }

  //--- construct and add a record of the transfer
  //--- which includes the ID of associated node
  vtkNew<vtkDataTransfer> transfer0;
  transfer0->SetTransferID(this->GetDataIOManager()->GetUniqueTransferID());
  transfer0->SetTransferNodeID(node->GetID());
  transfer0->SetSourceURI(source);
  transfer0->SetDestinationURI(dest);
  transfer0->SetHandler(handler);
  transfer0->SetTransferType(vtkDataTransfer::RemoteDownload);
  transfer0->SetTransferStatus(vtkDataTransfer::Idle);
  transfer0->SetCancelRequested(0);
  //--- Add the data transfer to the collection, and
  //--- the resulting mrml call will trigger an event
  //--- that causes GUI to refresh.
  this->AddNewDataTransfer(transfer0.GetPointer(), node);
  this->GetDataIOManager()->InvokeEvent(vtkDataIOManager::RefreshDisplayEvent);

  vtkDebugMacro("QueueRead: asynchronous enabled = " << this->GetDataIOManager()->GetEnableAsynchronousIO());

  if (this->GetDataIOManager()->GetEnableAsynchronousIO())
  {
    vtkDebugMacro("QueueRead: Schedule an ASYNCHRONOUS data transfer");
    //---
    //--- Schedule an ASYNCHRONOUS data transfer
    //---
    vtkNew<vtkSlicerTask> task;
    task->SetTypeToNetworking();
    transfer0->SetTransferStatus(vtkDataTransfer::Pending);
    task->SetTaskFunction(this, (vtkSlicerTask::TaskFunctionPointer)&vtkDataIOManagerLogic::ApplyTransfer, transfer0.GetPointer());

    // Schedule the transfer
    if (!this->GetApplicationLogic()->ScheduleTask(task.GetPointer()))
    {
      transfer0->SetTransferStatus(vtkDataTransfer::CompletedWithErrors);
      return 0;
    }
  }
  else
  {
    vtkDebugMacro("QueueRead: Schedule a SYNCHRONOUS data transfer");
    //---
    //--- Execute a SYNCHRONOUS data transfer
    //---
    transfer0->SetTransferStatus(vtkDataTransfer::Running);
    this->ApplyTransfer(transfer0.GetPointer());
    transfer0->SetTransferStatus(vtkDataTransfer::Completed);
    // now set the node's storage node state to ready
    vtkDebugMacro("QueueRead: setting storage node state to transferdone: " << dnode->GetNthStorageNode(storageNodeIndex)->GetURI());
    if (dnode->GetNthStorageNode(storageNodeIndex)->GetNumberOfURIs() == 0)
    {
      // done
      dnode->GetNthStorageNode(storageNodeIndex)->SetReadStateTransferDone();
    }
  }
  //  this->DebugOff();

  // loop over any other files in the storage node
  for (int n = 0; n < dnode->GetNthStorageNode(storageNodeIndex)->GetNumberOfURIs(); n++)
  {
    const char* sourceN = dnode->GetNthStorageNode(storageNodeIndex)->GetNthURI(n);
    const char* destN = dnode->GetNthStorageNode(storageNodeIndex)->GetNthFileName(n);

    vtkNew<vtkDataTransfer> transfer1;
    transfer1->SetTransferID(this->GetDataIOManager()->GetUniqueTransferID());
    transfer1->SetTransferNodeID(node->GetID());
    transfer1->SetSourceURI(sourceN);
    transfer1->SetDestinationURI(destN);
    // use one handler for all files in the storage node
    transfer1->SetHandler(handler);
    transfer1->SetTransferType(vtkDataTransfer::RemoteDownload);
    transfer1->SetTransferStatus(vtkDataTransfer::Idle);
    transfer1->SetCancelRequested(0);
    this->AddNewDataTransfer(transfer1.GetPointer(), node);
    this->GetDataIOManager()->InvokeEvent(vtkDataIOManager::RefreshDisplayEvent);

    if (this->GetDataIOManager()->GetEnableAsynchronousIO())
    {
      vtkDebugMacro("QueueRead: Schedule an ASYNCHRONOUS data transfer, n = " << n);
      vtkNew<vtkSlicerTask> task;
      task->SetTypeToNetworking();
      transfer1->SetTransferStatus(vtkDataTransfer::Pending);
      task->SetTaskFunction(this, (vtkSlicerTask::TaskFunctionPointer)&vtkDataIOManagerLogic::ApplyTransfer, transfer1.GetPointer());

      // Schedule the transfer
      if (!this->GetApplicationLogic()->ScheduleTask(task.GetPointer()))
      {
        transfer1->SetTransferStatus(vtkDataTransfer::CompletedWithErrors);
        return 0;
      }
    }
    else
    {
      vtkDebugMacro("QueueRead: Schedule a SYNCHRONOUS data transfer, n = " << n);
      transfer1->SetTransferStatus(vtkDataTransfer::Running);
      this->ApplyTransfer(transfer1.GetPointer());
      transfer1->SetTransferStatus(vtkDataTransfer::Completed);
      // now set the node's storage node state to ready
    }
  }
  if (dnode->GetNthStorageNode(storageNodeIndex)->GetNumberOfURIs() > 0 && //
      !this->GetDataIOManager()->GetEnableAsynchronousIO())
  {
    vtkDebugMacro("QueueRead: setting storage node state to transferdone after synchronous transfer of all files: " << dnode->GetNthStorageNode(storageNodeIndex)->GetURI());
    dnode->GetNthStorageNode(storageNodeIndex)->SetReadStateTransferDone();
  }

  return 1;
}

//----------------------------------------------------------------------------
int vtkDataIOManagerLogic::QueueWrite(vtkMRMLNode* node)
{
  //--- do some node nullchecking first.
  if (node == nullptr)
  {
    vtkErrorMacro("QueueWrite: null input node!");
    return 0;
  }
  vtkMRMLStorableNode* dnode = vtkMRMLStorableNode::SafeDownCast(node);
  if (dnode == nullptr)
  {
    vtkErrorMacro("QueueWrite: unable to cast input mrml node " << node->GetID() << " to a storable node");
    return 0;
  }

  if (dnode->GetStorageNode() == nullptr)
  {
    vtkErrorMacro("QueueWrite: unable to get storage node from the storable node " << dnode->GetID() << ", returning");
    return 0;
  }
  //--- find the storage node in scheduled state
  int storageNodeIndex = -1;
  for (int i = 0; i < dnode->GetNumberOfStorageNodes(); i++)
  {
    if (dnode->GetNthStorageNode(i)->GetWriteState() == vtkMRMLStorageNode::Scheduled)
    {
      storageNodeIndex = i;
      vtkDebugMacro("QueueWrite: found a scheduled storage node at index " << i);
      break;
    }
  }
  if (storageNodeIndex == -1)
  {
    vtkErrorMacro("QueueWrite: Could not find a scheduled storage node.");
    return 0;
  }

  //--- if handler is good and there's enough cache space, queue the read
  vtkURIHandler* handler = dnode->GetNthStorageNode(storageNodeIndex)->GetURIHandler();
  if (handler == nullptr)
  {
    vtkErrorMacro("QueueWrite: null URI handler!");
    return 0;
  }
  else
  {
    vtkDebugMacro("QueueWrite: got the handler");
  }
  if (this->DataIOManager == nullptr)
  {
    vtkErrorMacro("QueueWrite: DataIOManager is null");
    return 0;
  }

  vtkCacheManager* cm = this->GetDataIOManager()->GetCacheManager();
  if (cm == nullptr)
  {
    vtkErrorMacro("QueueWrite: CacheManager is null");
    return 0;
  }

  // Get the number of filenames and URIs associated with this storage node.
  // (assuming they should be equal)
  int numFiles = dnode->GetNthStorageNode(storageNodeIndex)->GetNumberOfFileNames();
  int numURIs = dnode->GetNthStorageNode(storageNodeIndex)->GetNumberOfURIs();
  //--- Note: the storageNode's FileName is repeated in its FileList, as
  //--- FileListMember0 *if* there are multiple files for the dataset.
  //--- However, the storageNode's URI is *not* repeated in its URIList
  //--- as URIListMember0. Would be nice if these things were the same.
  //--- but for now, respect the implementation: the URIList will be one
  //--- entity shorter than the FileNameList.

  std::string src;
  std::string dst;
  if (numFiles == 0)
  {
    //--- numFiles will be 0 if there's just one file in the storage node.
    //--- (no additional files in the list.)
    //--- adjust numFiles so we move thru the loop below at least once.
    src = dnode->GetNthStorageNode(storageNodeIndex)->GetFileName();
    dst = dnode->GetNthStorageNode(storageNodeIndex)->GetURI();
    numFiles = 1;
  }

  if (numFiles != (numURIs + 1))
  {
    vtkErrorMacro("QueueWrite: Storage node has different number of FileNames and URIs.");
    return 0;
  }

  std::vector<std::string> pathComponents;

  // schedule the write of each
  for (int n = 0; n < numFiles; n++)
  {
    if (n == 0)
    {
      //--- here we need to join the cache path to the filename.

      src = dnode->GetNthStorageNode(storageNodeIndex)->GetFileName();
      dst = dnode->GetNthStorageNode(storageNodeIndex)->GetURI();
    }
    else
    {
      src.clear();
      dst.clear();
      pathComponents.clear();
      vtksys::SystemTools::SplitPath(cm->GetRemoteCacheDirectory(), pathComponents);
      pathComponents.emplace_back(dnode->GetNthStorageNode(storageNodeIndex)->GetNthFileName(n));
      src = vtksys::SystemTools::JoinPath(pathComponents);
      dst = dnode->GetNthStorageNode(storageNodeIndex)->GetNthURI(n - 1);
    }
    //--- Construct and add a record of the transfer
    //--- which includes the ID of associated node
    vtkNew<vtkDataTransfer> transfer;
    transfer->SetTransferID(this->GetDataIOManager()->GetUniqueTransferID());
    transfer->SetTransferNodeID(node->GetID());
    transfer->SetSourceURI(src.c_str());
    transfer->SetDestinationURI(dst.c_str());
    transfer->SetHandler(handler);
    transfer->SetTransferType(vtkDataTransfer::RemoteUpload);
    transfer->SetTransferStatus(vtkDataTransfer::Idle);
    transfer->SetCancelRequested(0);
    this->AddNewDataTransfer(transfer.GetPointer(), node);
    this->GetDataIOManager()->InvokeEvent(vtkDataIOManager::RefreshDisplayEvent);

    vtkDebugMacro("QueueWrite: asynchronous enabled = " << this->GetDataIOManager()->GetEnableAsynchronousIO());

    if (this->GetDataIOManager()->GetEnableAsynchronousIO())
    {
      vtkDebugMacro("QueueWrite: Schedule an ASYNCHRONOUS data transfer");
      //---
      //--- Schedule an ASYNCHRONOUS data transfer
      //---
      vtkNew<vtkSlicerTask> task;
      task->SetTypeToNetworking();
      transfer->SetTransferStatus(vtkDataTransfer::Pending);
      task->SetTaskFunction(this, (vtkSlicerTask::TaskFunctionPointer)&vtkDataIOManagerLogic::ApplyTransfer, transfer.GetPointer());

      // Schedule the transfer
      if (!this->GetApplicationLogic()->ScheduleTask(task.GetPointer()))
      {
        transfer->SetTransferStatus(vtkDataTransfer::CompletedWithErrors);
        return 0;
      }
    }
    else
    {
      vtkDebugMacro("QueueWrite: Schedule a SYNCHRONOUS data transfer");
      //---
      //--- Execute a SYNCHRONOUS data transfer
      //---
      transfer->SetTransferStatus(vtkDataTransfer::Running);
      this->ApplyTransfer(transfer.GetPointer());
      this->GetDataIOManager()->InvokeEvent(vtkDataIOManager::RefreshDisplayEvent);
      transfer->SetTransferStatus(vtkDataTransfer::Completed);
      // now set the node's storage node state to ready
      dnode->GetNthStorageNode(storageNodeIndex)->SetWriteStateTransferDone();
    }
  }
  return 1;
}

//----------------------------------------------------------------------------
void vtkDataIOManagerLogic::ApplyTransfer(void* clientdata)
{

  //--- node is on the input
  if (clientdata == nullptr)
  {
    vtkErrorMacro("No transfer target was found");
    return;
  }

  //--- get the DataTransfer from the clientdata
  vtkDataTransfer* dt = reinterpret_cast<vtkDataTransfer*>(clientdata);
  if (dt == nullptr)
  {
    vtkErrorMacro("ApplyTransfer: data transfer is null");
    return;
  }

  // assume synchronous io if no data manager exists.
  int asynchIO = 0;
  vtkDataIOManager* iom = this->GetDataIOManager();
  if (iom != nullptr)
  {
    asynchIO = iom->GetEnableAsynchronousIO();
  }

  vtkMRMLNode* node = this->GetMRMLScene()->GetNodeByID((dt->GetTransferNodeID()));
  if (node == nullptr)
  {
    vtkErrorMacro("ApplyTransfer: can't get mrml node from transfer node id " << dt->GetTransferNodeID());
    return;
  }

  const char* source = dt->GetSourceURI();
  const char* dest = dt->GetDestinationURI();
  if (dt->GetTransferType() == vtkDataTransfer::RemoteDownload)
  {
    //---
    //--- Download data
    //---
    vtkURIHandler* handler = dt->GetHandler();
    if (handler != nullptr && source != nullptr && dest != nullptr)
    {
      if (asynchIO && dt->GetTransferStatus() == vtkDataTransfer::Pending)
      {
        dt->SetTransferStatusNoModify(vtkDataTransfer::Running);
        this->GetApplicationLogic()->RequestModified(dt);
        handler->StageFileRead(source, dest);
        dt->SetTransferStatusNoModify(vtkDataTransfer::Completed);
        this->GetApplicationLogic()->RequestModified(dt);

        vtkMRMLStorableNode* storableNode = vtkMRMLStorableNode::SafeDownCast(node);
        if (!storableNode)
        {
          vtkErrorMacro("ApplyTransfer: could not get storable node for scheduled data transfer");
          return;
        }
        // find the storage node that's been scheduled  and we're working on it
        int storageNodeIndex = -1;
        for (int i = 0; i < storableNode->GetNumberOfStorageNodes(); i++)
        {
          if (storableNode->GetNthStorageNode(i)->GetReadState() == vtkMRMLStorageNode::Transferring && //
              strcmp(storableNode->GetNthStorageNode(i)->GetURI(), source) == 0)
          {
            vtkDebugMacro("ApplyTransfer: found a working storage node who's uri matches source " << source << " at " << i);
            storageNodeIndex = i;
            break;
          }
        }
        if (storageNodeIndex == -1)
        {
          vtkErrorMacro("ApplyTransfer: unable to find a storage node in scheduled state.");
        }
        vtkMRMLStorageNode* storageNode = storableNode->GetNthStorageNode(storageNodeIndex);
        if (!storageNode)
        {
          vtkErrorMacro("ApplyTransfer: no storage node for scheduled data transfer");
          return;
        }
        storageNode->SetDisableModifiedEvent(1);
        // let the storage node know that the remote transfer is done
        vtkDebugMacro("ApplyTransfer: setting storage node read state to transfer done for uri " << storageNode->GetURI());
        storageNode->SetReadStateTransferDone();
        storageNode->SetDisableModifiedEvent(0);
        this->GetApplicationLogic()->RequestReadFile(node->GetID(), dest, 0, 0);
      }
      else
      {
        vtkDebugMacro("ApplyTransfer: stage file read on the handler..., source = " << source << ", dest = " << dest);
        handler->StageFileRead(source, dest);
      }
    }
  }
  else if (dt->GetTransferType() == vtkDataTransfer::RemoteUpload)
  {
    //---
    //--- Upload data
    //---
    vtkURIHandler* handler = dt->GetHandler();
    if (handler != nullptr && source != nullptr && dest != nullptr)
    {
      if (asynchIO && dt->GetTransferStatus() == vtkDataTransfer::Pending)
      {
        dt->SetTransferStatusNoModify(vtkDataTransfer::Running);
        this->GetApplicationLogic()->RequestModified(dt);
        handler->StageFileWrite(source, dest);
        dt->SetTransferStatusNoModify(vtkDataTransfer::Completed);
        this->GetApplicationLogic()->RequestModified(dt);

        vtkMRMLStorableNode* storableNode = vtkMRMLStorableNode::SafeDownCast(node);
        if (!storableNode)
        {
          vtkErrorMacro("ApplyTransfer: Upload: could not get storable node for scheduled data transfer");
          return;
        }
        // find the storage node that's scheduled
        int storageNodeIndex = -1;
        for (int i = 0; i < storableNode->GetNumberOfStorageNodes(); i++)
        {
          if (storableNode->GetNthStorageNode(i)->GetWriteState() == vtkMRMLStorageNode::Scheduled)
          {
            storageNodeIndex = i;
          }
        }
        if (storageNodeIndex == -1)
        {
          vtkErrorMacro("ApplyTransfer: upload: unable to find a storage node in scheduled state.");
        }
        vtkMRMLStorageNode* storageNode = storableNode->GetNthStorageNode(storageNodeIndex);
        if (!storageNode)
        {
          vtkErrorMacro("ApplyTransfer: Upload: no storage node for scheduled data transfer");
          return;
        }
        storageNode->SetDisableModifiedEvent(1);
        storageNode->SetWriteStateTransferDone();
        storageNode->SetDisableModifiedEvent(0);
      }
      else
      {
        vtkDebugMacro("ApplyTransfer: Upload: stage file write on the handler, source = " << source << ", dest = " << dest);
        handler->StageFileWrite(source, dest);
      }
    }
    else
    {
      vtkErrorMacro("ApplyTransfer: Upload: either no handler, or source or dest are null.");
    }
  }
  else
  {
    vtkErrorMacro("ApplyTransfer: unknown transfer type " << dt->GetTransferType());
  }
}

//----------------------------------------------------------------------------
void vtkDataIOManagerLogic::ProgressCallback(void* vtkNotUsed(who))
{

  //---TODO: figure out how to make this guy work and wire him into the rest of the mechanism
  //    TransferNodePair *lnp = reinterpret_cast<TransferNodePair*>(who);
  //--- get a pointer back to DataIOManagerLogic (?) dunno.
  //--- use its RequestModified method to call update on the DataIOManager (?)
  // lnp->first->RequestModified(lnp->second);
}
